Selective and antiparasitic receiving system



June 25, 1929. Y. MARREC 1,718,794

SELECTIVE AND ANTIPARASITIC RECEIVING SYSTEM Filed Aug. 8, 1923 Patented June 25, 1929.

UNITED STATES PATENT OFFICE.

Yvns MARREC', OF LONDON, ENGLAND, nssrenon r0 rmnnnc LIMITED, or LONDON, n. 0., ENGLAND.

SELECTIVE AND ANTIPABASITIC RECEIVING SYSTEM.

Application filed August 8,1923, Serial No. 656,450, and in Great Britain June 19, 1923.

This invention relates to selecting and parasite and interference eliminating meth ods and appa 'atus for electromagnetic waves or electric currents of a constant frequency in which. method and apparatus sustained oscillations are generated in stages by means of circuits sufficiently aperiodic to act as amplifying circuits and at the same time be the seat of sustained oscillationof definite frequency; and more particularly to methods of this type applicable to all receiving devices for currents of constant frequency, that is, to all receivers for electromagnetic waves, characterized by the simultaneous utilization of one or' more three-electrode valves disposed in the circuit of the sustained oscillations, to be received, and suitably regulated in order to serve simultaneously 1. As an amplifying relay;

As a producer of sustained oscillations whereof the current has a frequency very different from that of the signal to be received, for example, a multiple or sub-multiple of the frequency of the signal, and is super-imposed on the currents due to the signals and those due to the parasite effects, thus forming two groups of oscillations, one corresponding to the signal and the others corresponding to the parasite effects;

3. As a limiter of the amplification of the currents received by the effect of saturation produced by the starting of sustained oscillations;

a. As an eliminating device for parasite oscillations, thus permitting only the recep- -tion of the oscillations due to the signals.

The present invention has for its object an improved method and apparatus of this type in which, besides the amplification, two resultanls of the sustained oscillations are obtained, one with the signals, on the one hand, and the other with the parasites or interferences, on the other hand.

In this method, after the waves have been preliminarily detected by a known method,

they are sent into one or more aperiodic ampli'tying circuits, comprising for example tln'ee-electrode valves, and mutually reacting through transformers, thereby producing a double effect, firstly the amplification of the detected waves, and secondly the production of local low frequency oscillations whose frequency is determined by the suitable choice of the characteristics of one or more of the aperiodic circuits which are however tunedto the frequency of thelocal oscillation sought for, the local waves being superposed upon the received waves comprising parasite effects or actual transmitted waves, thereby producingtwo resulting waves of a different character. The resultant oscillations then proceed into a certain number of low frequency circuits tuned to the note of the wave resulting from the superposition of the message which itis proposed to be received upon the local sustained oscillation, the saturation of the threeelectrode valves in the low frequency circuits being controlled by a rheostat which reduces the heating current of the filaments, so as to regulate the amplification due to the said resonance circuits and to constitute, so to speak, filtering arrangement which will ontirely eliminate the waves due to parasite effects, in the known manner. The signals thus isolated are finally suitably amplified and received by suitable apparatus such as telephone listening devices, telegraph recorders, and the like.

The resonance circuits put successively in series are not for the purpose of operating as amplifying relays properly so called, but particularly to act as filters of the currents to be received, thesecircuitsbeing so constituted as to be bad circuits for all the oscillations which have not the frequency for which they are tuned. On the other hand, the valves inserted in thesecircuits have for their purpose to limitsimultaneously the amplitude of the currents, and to produce a sutlicient aniplification, in order to reamplify the currents to be received after these successive filtrations.

By increasing the number of amplifying stages and by limiting the amplitudeof each stage, the amplified resultant and the saturation of the plate circuits are adjusted to be the same for the parasitic or interference oscillations as for the signal oscillations; this is Obtained byudecreasing the heating, thereby producing on the amplification a reduction which is compensatedforlby the addition of other amplifying circuits. i V

In practice, although this method works well, it is found that, when it is intended to filter out comparatively weak signals from powerful parasitesmwing to the fact that, in I order to generate the sustained oscillations of suflicient amplitude, it is necessary to use more than three stages of valves in the aperiodie circuits, the large number of amplifying stages then causes the sustained oscillations to become troublesome and the result is not so good and not so reliable as to be thoroughly satisfactory.

I have found that, by slight modification of the method above described, I can obtain, even in the case of weak signals (from transatlantic stations, for instance) and in the presence of numerous andvery strong local parasite interferences, such as close neighbouring transmitting-stations emitting powerful waves of various wave length, electric trains and trams, etc., a perfect elimination of all interfering oscillations, as well as a greater amplification of the signals themselves, so that long distance signals can be easily received and recorded by means of an ordinary frame aerial.

1 According to this invention, a parasite or interference eliminating method and apparatus'of the type described is modified and adjusted, according to the following requirements, whichmust be satisfied in order to obtain satisfactory results in the adverse conditions mentioned;

- (1') The heating rheostats of the aperiodic valves are adjusted so as to reduce the plate saturation-current, but only moderately, so that the aperiodic circuits work simultaneously as generators of sustained oscillations and as amplifying devices.

(2) The heating rheostats of the resonance amplifiers are adjusted so that the plate saturation-current is sufiiciently reduced to limit the amplification and at the same time obtain the desired selection.

(3) The use of-a number of aperiodic circuits greater than that necessary for receiving in ordinary conditions, allows of the generation of sustained oscillations and of their sufficient amplification, but introduces interferences which must be guarded against.

' (4) The heating battery and the high ten sion battery of the valves of the parasiteeliminating' apparatus are entirely independent of thebatteries'of the valves of the receiving apparatus proper, in order to avoid oscillations which might occur in inter-connected circuits and to render the several circuits mutually independent so that the adjustment of xonecircuit will not upset the adjustment of the others, l r

j (5) The positive terminals of the high tension batteries or accumulators are connected to one another and to an earthed metallic mass.

The reduction of saturation current is necessarily accompanied by a reduced amplification which must be compensated for by a larger '"number of valve circuits than would be the case if the saturation current were not so reduced. The larger number of valve circuits introduces interferences which require special precautions, such as the use of entirely independent batteries and the earthing of all the positive terminals, (4) and (5) above. By this means,

one is able to suppress, when they are troublesome, the sustained oscillations due to the great number of amplifying stages used.

Vhcn the receiving and parasite-climinat ing apparatus is arranged and adjusted as above-stated, a complete elimination of parae sitic and interfering disturbances and a. per fect selection of signals is obtained, even in the unfavourable circumstances described, the signals being of a distinctness and loudness which has been hitherto never obtained, and mechanical recording (by means of the ordinary Morse inker, for instance) being not only feasible, but quite easy and reliable.

If a greater amplitude is required, a cascade of resonant amplifiers may be added, the valves being regulated as in (2) above.

The oscillations produced by the utilization of a large number of.aperiodic stages could be produced by a low frequency heterodyne acting by induction upon the low frequency receiving circuits, provided that the currents are sufficiently amplified.

In one particular apparatus. constructed according to this invention, we tind that the resonance transformers must be at least 8 cm. apart if they are in the same plane, and 5 em. if in perpendicular planes; we have also found that the best results are obtained when the transformers in the resonant circuits are of special shape and constructed as follows:

The magnetic circuit consists of 250 stampings, each 0.2 mm. thick, insulated with shellac varnish; the primary winding consists of 900 turns of 0.45 mm.. and the secondary consists of 2700 turns of 0.25 mm., copper wire, double silk insulated. The secondary is wound in two separate equal portions, one on each side of the primarv: the space between the primary and the secondary being 1 mm., including the insulation.

The above modifications, although slight, are nevertheless of the greatest importance practically, as by them results are obtained which could not be obtained without them.

Instead of proceeding as above, one may amplify the resultants of the waves comprising both the signals and the parasites by stages of low frequency aperiodic circuits. and subsequently select the amplified oscillations by resonant circuits tuned to the tinal frequency of the received signals and comprising valves or the like with relatively low heating, so as to weaken the parasites by saturation or other equivalent means, the signals 7 not being inconveniently attenuated, owing to the resonance of the circuits.

The improved selecting and parasite-eliminating apparatus which is the object of the present invention constitutes a reliable device l of relatively small cost, acting as an extremely sensitive telemechanical relay. It can therefore be used for re-transmittin; the received signals to further receiving stations.

The small cost of the combined receiving and 1 lUU ltl.)

. ceptible of realization without the improve ments forming the object of this invention. This is a far-reaching development of wiretelegraphy as. it suppresses the powerful and costly transmitting installations and permits the use of small transmitting installations working in series at a small radius. This development is not only very economical but also very cflicient forthe reason that the transmission waves of a big transmitting station travel in a circle of a big radius and can be intercepted by everybody in the periphery of the circle. The small station having a small radius of action brings wireless telegraphy to the point that has so much been looked forward to, of thcsending of a wircless wave in a given direction.

For instance, a large station in London for transmission to a distance of too miles can be heard not only in Scotland but also in Paris, France, but if a series of small stations of 60 miles would be installed in a chain from London to Scotland, the message sent from Lon don would be heard in Scotland but could not be intercepted inFrance.

As the electric wave travels at such speed that it can be considered instantaneous, the speed of such transmissions are similar in both cases and the cost of installing the chain of small stations will be always inferior to the installation of one largestation.

In other directions, as a teleniechanical re lay, the improved receiving apparatus, the objectof this invention, can be put to amultiplicity of uses,for instance, the guiding of a pilotless aeroplane by means of wireless, a motor boat steered by wireless, etc. This is obtained by wireless teleniechanics but regardless of success received in short distances the definite application of it is impossible as the atmospheric interferences can influence the receiving apparatus and pervert the results.-

Most actually existing transmitting stations (owing to imperfections in transmitting apparatus) are open to the drawback that, in transmitting the signals, the receivers hear not only the signals but also the cutoii between the dash and dot of the signals, and it is necessary to be very proficient in Morse reading to distinguish the dashes and dots of the signals from the compensation sounds.

The anti-parasite method and apparatus, the object of this invention, not only is effective in separating these two sounds and use, as one wishes, one or the other sound, but it also can utilize these defects of transmit ing stations for controlling purposes Experience shows that, in this manner, all

parasites are suppressed between the signals.

but in case the parasite is very powerful and happens to fall just on the signal, it deforms this signal, so that, when. registered on a tape, for instance, it is. very distinctive as it cuts only the signals. If, at the same time, a second registering apparatus, tuned to the compensation waves, will inscribe the intervals between the signals, leaving empty the spaces where the signals are inscribed, the parasite is rendered visible.

In this manner, the existing defects of transmitting stations are utilized for controlling purposes, and it is possible to mod ify existii'ig registering apparatus in such a Way that it will work simultaneously on the same tape.

Numerous methods have been also proposed for effecting the simultaneous transmission of telegraphic signals on the same line; particularly it has been proposed to send simultaneously on the same line signals consisting of oscillatingelectric cur rents of constant frequency, and to separate at the receiving end the signals of dillerentfrequencies by means of suitable selecting dcvices. In practice, however, it is found that the oscillations are interfered with by auxiliary accidental undulations superposed to the signals, which distort them and prevent their reliable selection at the receiving end, unless a suitable reliable selecting devico be available. Such a selecting device is found in the improved receiver, the object of this invention, a series of which may be used at the receiving end, each receiver being tuned to the corresponding frequency it is intended it should receive, and registering or rc-trans mitting the signals, without in the least being affected by the signals of different frequencies to the oneit selects;

Referring to the appended drawings which illustrate as examples the connection of auti-- parasitic radio-telegraphic receiving :5 stems, according to my invention Fig. 1 shows the disposition of the antiparasitic system for sustained constant frequency oscillations: i

Fig. 2 shows the disposition of the antiparasitic system as arranged for working with compensating waves. I i

In Fig. 1 a, a are the reception terminals for the detected currents; b are primaries and c are secondaries of low frequency aperiodic transforn'iers (ratio 1/3), of which (Z are the closed magnetic circuits; and g are constant capacities of .001 microfarad; 7 is the heating resistance of 3 valves; 2' and j are the primaries and secondaries respectively of resonance transformers of which it are the (proferably adjustable) open magnetic circuits (the three transformers are tuned to the same frequency) Zare condensers of constant capacity .020 microfarad; m is the heating resistance; n is the terminal for collecting the selected currents; 0 is the earth connection.

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This apparatus, connected on any ordinary amplifier, is sufficient to vary the heating to obtain the sought results. According to the nature of aperiodic transformers utilized, the condensers e, .f, 9 must be either modified or done away with.

In Fig. 2,1 and P represent the resonant low' frequency circuits tuned to the sending the same note, but it is evident that the results are not changed if one tunes the three circuits, on a different note, either in altering the self-induction or the capacity of these circuits. y

In the above description, by parasite is meant any interference effect due either to electro-magnetic waves or electriccurrents. Also, by battery, is meant any source of potential difference, such as a battery of accumulators, I a

What I claim and desire to secure by Letters Patent is 1 1. In a signal receiving apparatus, a plurality of groups ofcascaded electron tubes each group having input and output circuits,

of electron tubes with the input and output circuits of said second group of electron tubes coupled by means selective to a definite frequency, said first group of electron tubes having circuits arranged for'the generation of oscillations for combination with a selected frequencyfrom the range of frequencies for which said first mentioned group of electron tubes is responsive, whereby the beat frequency may be selectively amplified by said Seeond-group of electron'tubes and parasitic interference. therewith prevented.

- 2. A signal receiving apparatus comprising a plurality of electron tubes, said electron tubes being divided into independent groups having input and output circuits, a signal receiving circuit connected with the input .circuit of the first group of electron tubes, circuits interposed between the several tubes constituting the first group and adjusted to respond to. a'band of frequencies and arranged to develop oscillations for combination with a signalling frequency within said band of frequencies for the develo ment of a resultant beat frequency, a secon group of electron tubes having means connected therewith for the selective amplification of the resultant beat frequency, and means for controlling the amplification factor of the electron tubes in said last mentioned group for preventing interference from parasitic oscillations.

3. A telegraphic receiving system comprising a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, means coupling the output circuit of one electron tube with the input circuit of a succeeding electron tube, said electron tubes being divided into two groups with the means coupling the output and input circuits of the tubes of one group adjusted to a definite band of frequencies and the input and output circuits of the electron tubes included in said second group adjusted selectively for a particular frequency derived from said band of frequencies, and means for reducing the normal electron emission of the filaments of the electron tubes in said second group for the reception of signals whereby parasitic oscillations in said electron tube circuits are prevented.

4. A telegraphic signal receiving apparatus, comprising a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, said electron tubes being divided into two groups, transformers responsive to a definite band of frequencies interconnecting said input and output circuits of the first group of electron tubes, a responsive device connected in the output circuit of the last group of electron tubes, said last group of electron tubes having the circuits thereof adjusted to a particular frequency derived from a selected frequency in the band of frequencies for which said first mentioned group of electron tubes is adjusted and a filament control circuit for the filament electrodes ofsaid last mentioned group of electron tubes for maintaining the electron emitting temperature thereof below normal for the prevention of parasitic oscillations.

5. In a telegraphic signal receiving apparatus, a plurality of groups of electron tubes each of said tubes having grid, filament and plate electrodes, input and output circuits for each of said tubes, means responsive to a definite band of frequencies interconnecting the output circuit of one electron tube with the input circuit of a succeeding electron tube in one of said groups with two of said groups of tubes connected in series with the output circuit of the first group and forming separate branch circuits arranged to control separate responsive devices, means for selectively tuning the input circuits of said two groups of electron tubes to different frequencies, respectively derived from selected frequencies within the band of frequencies to which said first group is responsive, and means for maintaining the electron emission of all of said electron tubes in said last two groups below normal for the reception of signalling energy, whereby parasitic oscillations are prevented.

6. In a telegraphic signal receiving apparatus, a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes with the output circuit of one electron tube coupled with the input circuit of a succeeding electron tube, said. electron tubes be in arran 'ed in a luralit T of rou as one of said groups having its circuit arranged for the production of oscillations and responsive to a plurality of signalling frequencies, and the others of said groups having the input circuits of the several tubes thereof selectively tuned to resultant frequencies respectively derived by the combination of separate incoming signalling oscillations and the locally generated oscillations, and means in said last mentioned groups of tubes whereby the electron emission thereof may be maintained below normal for the reception of signalling energy while preventing parasitic interference.

In testimony whereof, I affix my signature.

YVES MARREO. 

